Spring-rewinding means



July 1930. c HA L SPRING REWINDING MEANS Filed April 12. 1928 Inventor":

Chester I. Hal I, yW

His Attorney Patented July 15, 1930 vmural) STATES PATENT OFFICE CHESTER I. HALL, OF FORT WAYNE, INDIANA, ASSIGNOB TO GENERAL ELECTRIC COMPANY, A COBPOILATION 01' NEW YORK sramo-imwmnma MEANS Application filed April 12,

My invention relates t-Q-a- "onstant torque motive mechanism which is suitable for general application but, which is particularly adapted for use in spring driven clock movements where a small electric motor is employed for winding the spring.

The time keeping, qualities of the ordinary hand wound spring driven clock movement is impaired by reason of the fact that the clock escapement is required to regulate the speed between wide limits of the main spring tension. 'In the eight day clock for example, when the spring is fully wound, the escapement mechanism is subjected to considerably more tension than exists when the spring is nearly unwound. As a result the beatof the escapement tends to vary somewhat with the tension of the main spring. [This varying condition may be compensated for to some extent but at the expense of added complications and cost. To avoid the conditions above mentioned it has been proposed to maintain the clock spring wound to a substantially constant tension by automatic means, such as an electric motor, together with means dependent upon the condition of the spring for controlling the motor.

My invention relates to improvements in devices of the last mentioned group and its to principal object is to provide a simple, inexpensive but reliable mechanism for maintaining the clock spring wound to a very uniform tension. In carryin my invention into effect I provide means or regulating the speed of the rewindin motor in accordance with the movement 0 the clock hands, under-normal conditions, and in accordance with the counter-torque exerted by the spring. In the preferred form of my invention, a

differential gear .train is provided, one side of which is actuated by the clock hand shaft and the other by a rewinding motor of the induction disc, shaded-pole type. The gear collar, whose movement depends upon the difference in speeds of the two sides of the differential is geared to the shaded pole of the driving motor rotating it until due to the combined effect of the increasing counter torque and the torque reducing movement of the shaded pole, the motor slows down to a 1928. Serial No. 269,515.

speed at which the two sides of the differential are equal and opposite. Any reduction of the counter-torque of the main spring, due to movement of the clock hands, is accompanied by a torque or speed increasing movement of the shaded pole and vice versa. The differential therefore serves as a measure of the counter-torque of the spring and regulates the speed of the winding motor accordingl 00 Tie novel features which I believe to be characteristic ofmy invention, are pointed out in the appended claims. M invention itself, however, will best be un erstood by reference to the following s ecification when considered in connection wit the accompanying drawing in' which Fig. 1 is a diagrammatic illustration of a spring driven clock mechanism, the driving spring of which is rewound by an electricmotor whose speed is regulated in accordance with this invention.

Fig. 2 is an enlarged detail view illustrating one method of actuating the shaded pole, whereby the torque and speed of the motor are adjusted. Referring to the drawings in detail, 10 indicates the spring which drives the clock mechanism through gear 11, pinion 12 and shaft 13. Shaft 13 o crates the minute hand 14 and the hour han 14 through a suitable go back gear train 15. A standard spring escapement 16 regulates the movement of shaft 13 through shaft 17, vpinion 18 and gear 19 mounted on shaft 13.

The spring 10 is mounted with. its outer 35 end attached to gear 11 andits inner end attached to shaft 20', upon which gear ll-is loosely mounted. It is unwound by means of motor 21. Motor 21 includes a U-shaped magnetic frame 22, to the sides of which coil 9. 23 wound on core 23 and shadedpole 24 areattached. In the air gap between the core 23' and pole 24 a disc 25, of conducting ma-.

terial, is caused to rotate when'coil 23 is supplied with alternatin current. The al- 05 ternating flux created by t e current in coil 23 asses across the gap between 23 and 24 and is converted into a shifting flux by the short circuited coil 24 on pole 24. The amount of shifting of this flux, in a direction tangential I0:

to the direction of rotation, determines the speed and torque of the disc 25. The position in which coil 24 causes the greatest amount of shifting of the flux, in a torque producing direction, is that shown by full lines in Fig. 2. Any change from this position as for instance the position indicated by dotted lines in the same figure, reduces the tangential flux shift and thereby the speed of disc 25. Disc 25 is mounted on shaft 26 upon which Worm 27, engaging a gear 28, is also mounted. The rotation of disc 25 therefore, rewinds spring 10 through gear 28, shaft 29, pinion 30, gear 31 and shaft 20. The worm 25 makes this transmission irreversible so that in case the motor stops, due to an interruption in power or other causes, the spring will rontinue to drive the clock mechanism for a 1 onsiderable time.

As already stated, it is desirable to maintain the spring 10 at a constant tension. The speed of disc 25 must, therefore, be regulated substantially in accordance with the movement of the clock hands, under normal conditions and in accordance with the counter torque of the spring. For this purpose a differential 32 is used. The diii'erential 32 includes bevel gears 33 and 34, and pinions 35, engaging therewith, mounted inside of ring gear 36. Bevel gear 33 is mounted on gear 19 and is, therefore, dependent upon it for its movement. Gear 34 is mounted on a gear 37 driven by gear 38, shaft 39, pinion 40 and gear 41 on shaft 20. It is, therefore, evident that one side of the differential is driven in accordance with the unwinding of the spring 10 and the other side is driven, in an opposite direction, in accordance with the rewinding thereof. Any difference in the speeds of these two sides causes gear 36 to move. Gear 36 engages pinion 42 mounted on shaft 43. Shaft 43 drives worm 44, engaging gear 45, on shaded pole 24. Any movement of gear 36, therefore, changes the position of the winding 24 and thereby the speed of the disc 25. The gear ratio between the two ends of the clock spring and the two sides of the differential must, of course, be the same.

In operation the shaded pole is set at the full speed position of the motor when the spring is practically unwound. When power is supplied to the motor it starts at a high speed and gradually slows down, due to the combined effect of the increasing counter torque of the spring and the movement of the shaded pole in a torque reducing direction. A movement of the shaded pole when the spring is nearly wound has a greater effect uponthe speed of the motor than a corresponding movement at the unwound condition of the spring. It is therefore possible to so choose the rating of the motor, and the gear ratios, that the spring will be initially wound to a predetermined tension, will be held there under normal conditions, and will be rewound to that tension in case the motor stopped for a time and the spring became un wound through continued operation during that time.

In accordance with the provisions of the patent statutes, I have described the principle of operation of my invention together with the apparatus which I now consider to represent the best embodiment thereof, but I desire to have it understood that the apparatus shown and described is only illustrative and that the invention may be carried out by other means.

What I claim as new and desire to secure by Letters Patent of the United States, is:

1. In combination, a driving spring, a motor for continuously winding said spring including a disc armature, and a rotatable stator member capable of varying the torque exerted by said armature, and means for rotating said member so that the spring will be kept at a substantially constant tension.

2. In apparatus of the character described, a driving spring, an induction-disc type motor including a rotatively mounted shaded pole capable of varying the torque exerted by said motor for winding said spring, means responsive to the movement of said motor and the unwinding of the spring for rotating said pole so that the tension on said spring will be maintained substantially constant at a predetermined value.

3. In combination, a driving spring, a motor for continuously winding said spring in cludin a disc armature and a rotatable shade pole, the position of which determines the torque of said motor and differential gear means arranged to rotate said pole so that the spring will be wound to a predetermined tension and maintained substantially constant at that tension.

In witness whereof, I have hereunto set my hand this 9 day of April, 1928.

Y CHESTER I. HALL.

CERTIFICATE OF CORRECTION.

Patent No. 1,770,775. I Granted July 15, 1930, to

CHESTER I. HALL.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 1, line 88, for the word "unwound" read rewouud; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office. I

Signed and sealed this 9th day of September, A. D. 1930.

M. J. Moore, (Seal) Acting Commissioner of Patents.

CERTIFICATE OF CORRECTION.

Patent No. 1,770,775. I i Granted July 15, 1930, to

CHESTER I. HALL.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 1, line 88, for the word "unwound" read rewound; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 9th day of September, A. D. 1930.

l M. J. Moore, (Seal) Acting Commissioner of Patents. 

